The present invention relates to a composition for use in a dishwashing machine and a process for the use thereof.
Although modern dishwashing machines in most cases have numerous different washing programs, which differ with regards to the duration and temperature of the individual washing cycles, all washing programs essentially consist of the following basic steps: preliminary washing cycle, main cleaning cycle, one or more intermediate rinsing cycles, a clear rinsing cycle and drying. Whereas the machine dishwashing agent for bringing about the cleaning action is added at the start of the main cleaning cycle, during the clear rinsing an cycle special agents are used, e.g. clear rinsing agents. Clear rinsing agents are intended to ensure that when washing with water water droplets are not left behind on the washed articles which, after drying on, leave behind marks of substances dissolved/dispersed in the droplets.
These two functionalities, namely the cleaning action of the machine dishwashing agent and the described function of a clear rinsing agent, have hitherto been brought about using two separate charging or dosing devices and products charged or dosed at different points during the dishwashing cycle.
Apart from the use of clear rinsing agents, there is still a need for further substances evolving their activity during the washing or rinsing cycle, such as e.g. an antibacterial activity (e.g. cationic compounds or triclosan), silver protection agents (e.g. benzotriazole), an odorous action (fragrances, perfume), bleaching action/disinfection (chlorine bleaches), odour masking (e.g. polyvinylpyrrolidone), anti-coating agents and enzymes for additional purposes (e.g. lipase for removing grease and fat deposits in the dishwasher). However, modern dishwashers have no suitable charging systems for this purpose.
The aim of the present invention was consequently to combine in a single function the cleaning function and the function or functions of the substance or substances to be added during the clear rinsing cycle with a constant efficiency compared with the results obtainable with a separate charging or to permit the charging of substances other than the clear rinsing agent in the clear rinsing cycle.
DE-OS 20 65 153 and 20 07 413 disclose detergent blanks for use as detergents, in which it is inter alia provided that two components having a different functionality are combined. The structure comprises an enveloping shell, which is e.g. formed from two shell halves comprising a cleaning agent, as well as a cavity enclosed by the shells and which contains additives such as softeners, brighteners, etc.
British patent 1 390 503 discloses a liquid detergent containing capsules, which are insoluble in the composition, but release their content if the composition is diluted with water. This objective is achieved in that the capsules are coated with a substance having a poor solubility in water solutions with high ionic strength, but becoming soluble if the ionic strength is reduced by dilution. It is pointed out that this procedure can be used to incorporate materials in the liquid cleaning agent, which are unstable in the latter or would produce an instability if added directly. It is also proposed that this procedure be used in order to delay the release of a specific substance. Reference is made to use in machine dishwashing agents and it is proposed for the encapsulation of tribromosalicylanilide in order to stabilize the latter. The encapsulated material is released within two minutes following the dilution of the cleaning agent with water, i.e. in the main cleaning cycle.
U.S. Pat. No. 4,082,678 describes a fabric conditioning product comprising a closed container containing a releasable agent, which is used to make water-insoluble or non-dispersible an inner container located in the container and which is normally water-soluble or water-dispersible, the inner container is containing a fabric conditioner. The inner container is made from a substance, whose solubility in water is highly dependent on the ionic strength or the pH-value of the medium and the agent used for rendering the inner container insoluble is an agent for controlling the pH-value or ionic strength.
Japanese patent applications KOKAI 60-141705, 61-28440, 61-28441, 61-28596, 61-28597 and 61-28598 describe processes for the production of pH-sensitive microcapsules for use in detergents. The pH-sensitive coating is a copolymer of the following monomers:
A) at least one basic monomer of formula I: 
in which R is hydrogen or a methyl group, R1 and R2 in each case an alkyl group with 1 to 3 carbon atoms and x an integer from 1 to 4, B) at least one monomer, which is insoluble or difficultly soluble in water and
C) at least one water-soluble monomer.
It is stated that the polymers described are insoluble at a pH-value of 9.5 or higher and are soluble at a pH-value of 8.5 or lower. A description is given of different ingredients of cleaning agent compositions, which can be successfully and usefully coated with the polymers described. The aim of the invention described therein is that the substances only evolve their function during the rinsing cycle, protect the same up to the start thereof and then immediately release it. The use for dishwashing machines is not described.
A disadvantage of the solution described in these Japanese patent applications is that the enveloped particles are in direct contact with non-alkaline washing water at the start of the washing cycle which can lead to a partial dissolving of the protective envelope.
Japanese patent KOKAI 50-77406 discloses a washing aid surrounded by a water-soluble envelope obtained by mixing polyvinyl acetal dialkyl aminoacetate and at least one organic acid, which is solid at ambient temperature. This protective envelope serves to protect the washing aid during the main washing cycle and release it during rinsing cycles. The described compound reacts to a change of the pH-value between the main washing cycle and the rinsing cycle. The correspondingly enveloped particles are mixed with conventional pulverulent detergent. Here again the disadvantage of a possible partial dissolving of the protective envelope at the start of the washing cycle occurs.
European patent applications EP 284 191 A2 and 284 334 A2 disclose a water-soluble polymer film for the release of washing additives in the rinsing cycle of washing machines which, during the normal washing cycle, remains intact over a typical temperature range and rapidly dissolves in the rinsing cycle. It is pointed out that although the use of pH-sensitive coatings is known, said films are normally temperature-sensitive, so that they are not reliably stable during the different temperatures occurring in the washing cycle. The solution proposed is a pH-dependent material (which undesirably also has a positive temperature-dependent dissolving behaviour), which is combined with a material having a negative temperature-dependent dissolving behaviour. This combination is intended to guarantee that the coatings do not dissolve at the high temperatures at the start of the washing cycle (particularly the very high temperatures occurring in American machines). No reference is made to a use for machine dishwashing agents.
European patent application EP 481 547 A1 discloses multilayer machine dishwashing agent tablets with a core, a separating layer surrounding the core and an outer layer for the sequential release of the ingredients of the different layers. The aim of this tablet is to solve two different problems, namely 1) incompatible materials can be formulated together in a single tablet and released at different times in order to prevent mutual influencing and 2) compositions intended to evolve their functions at different times can be formulated in a single tablet.
An important disadvantage of this prior art is that for initiating the dissolving of the enveloping layer the temperature and/or in particular the contact time with the washing solution is used as the initiating factor, i.e. temperature-sensitive materials are used for the envelope material. As the temperature/time gradient in dishwashing machines can vary very widely as a function of the selected program, it is difficult, if not impossible, to select a material for the envelope which is usable for all possible programs of modern dishwashing machines. EP 481 547 A1 (p 7, lines 37 to 43) admits that the choice of the material of the enveloping layer must take account of equipment and program-specific details. Thus, the practical usability of the described products is significantly limited.
PCT application WO 95/29982 discloses a machine dishwashing agent with a delayed release of a clear rinsing agent in the form of a nonionic surfactant, which forms together with an inorganic builder salt a core particle, which is provided with a wax-like envelope in order to ensure the delayed release This envelope is a substance which does not melt at the operating temperatures encountered in the cleaning cycle, but which so gradually chemically disintegrates under alkaline pH-values that there is still left at the end of the main cleaning cycle an active clear rinsing agent quantity which is transferred into the clear rinsing cycle.
It is disadvantageous that the envelope is rendered soluble by chemical saponification under alkaline pH-values, so that the time at which the clear rinsing substance is released from the core is a function both of the temperature and the length of the main cleaning cycle. The patent application provides no teaching for the formulation of a product with which it is possible to release the clear rinsing agent only when the clear rinsing cycle arrives in all washing programs of any machine type. In addition, the core ingredient active as the clear rinsing agent is a nonionic surfactant, which is absorbed on an inorganic builder salt. This leads to inferior clear rinsing results, particularly with respect to marks on glass. The product is finally a mixture of granular detergent and granular clear rinsing agent particles.
In view of the prior art, the problem of the present invention is to provide a composition usable for most rinsing/washing programs of different dishwashing machine types and in each of these cases the substance or substances having only to evolve their action in the clear rinsing cycle are only released at the earliest at the start of the clear rinsing cycle. The aim is to achieve this without restricting the choice of the cleaning agents used, the substance or substances used for the clear rinsing cycle and other ingredients of the composition.
According to the invention this problem is solved with a solution characterized by a basic composition evolving its function essentially in the main cleaning cycle of the dishwashing machine; as well as at least one particle, with at least one core incorporating at least one substance, which evolves its function essentially in the clear rinsing cycle of the dishwashing machine and an envelope substantially completely surrounding the core or cores incorporating at least one compound, whose solubility increases with decreasing concentration of a specific compound in the surrounding medium. Agents are provided so that at the start of the clear rinsing cycle a significant dissolving of the envelope or a significant detachment of the envelope from the core or cores is prevented.
In an advantageous embodiment the concentration of the specific compound in the local environment of the particle or particles is sufficiently high up to the start of the clear rinsing cycle so that up to this time there is no significant dissolving of the envelope or significant detachment of the envelope from the core or cores.
Preferably the particle or particles are coated with a substance which, substantially independently of the concentration of the specific compound in the surrounding medium, dissolves or separates during the main rinsing cycle of the dishwashing machine.
The basic composition is preferably in the form of a tablet.
An embodiment of the invention proposes that the at least one particle is so placed in or on the tablet that the concentration of the specific compound in the local environment of the particle or particles is sufficiently high up to the complete dissolving of the tablet to prevent a significant dissolving of the envelope or a significant detachment of the envelope from the core or cores.
Preferably the particle or all the particles are received in at least one tablet cavity completely surrounded by the basic composition.
The at least one cavity can receive one or more particles having alone or together essentially the same volume as the cavity.
Preferably the at least one cavity has a larger volume than the or all the particles received in the particular cavity.
In an alternative of the invention the particle or particles are arranged loosely in the cavity interior.
In another alternative the particle or particles are fixed, preferably by an adhesive, in the cavity interior.
In a further embodiment the cavity is positioned substantially centrally in the tablet interior.
The invention also proposes that the tablet has a single, substantially spherical cavity.
According to the invention the cavity receives a single, substantially spherical particle, whose external diameter is smaller than the internal diameter of the cavity.
According to another embodiment the or all the particles are received in at least one cavity of the tablet, which is only partly surrounded by the basic composition.
Preferably the cavity is a depression in one of the surfaces of the tablet in which the particle or particles are at least partly received.
In a preferred embodiment the particle is so received in the cavity or depression that it does not project over the surface or surfaces of the tablet.
A special embodiment of the invention proposes that the cavity or depression only contains a single particle, whose volume and shape in the vicinity of the cavity or depression substantially coincides with the volume and shape of the cavity or depression and substantially completely fills the same.
Preferably the cavity or depression is parallel to one of the surfaces to which it opens or in which it is located and has a substantially circular cross-sectional surface.
The invention also proposes that the cavity or depression opens to the surface or surfaces only to the extent that the particle or particles received therein cannot pass through the opening or openings of the cavity or depression.
It is inventively preferred for the particle or particles to be loosely arranged in the cavity or depression.
In a further alternative the particle or particles are fixed in the cavity or depression, preferably by an adhesive.
According to an embodiment of the invention the basic composition incorporates at least one composition chosen from the group comprising machine dishwashing agent composition, water softener composition and washing intensifier composition.
In a preferred embodiment of the invention the envelope incorporates at least one compound which for the concentration of the specific compound at the end of the main cleaning cycle of the dishwashing machine is not or is only slightly soluble and at the concentration of the specific compound in the clear rinsing cycle has such an adequate solubility that in the clear rinsing cycle it is so substantially dissolved or detached from the core or cores that an at least partial escape of the core material into the clear rinsing cycle medium is possible.
Preferably the solubility of the compound increases with decreasing OHxe2x88x92 ionic concentration and therefore decreasing pH-value in the surrounding medium.
In particularly preferred manner the compound at a pH-value above 10 has little or no solubility and at a pH-value below 9 has an adequate solubility to ensure a substantially complete dissolving or detachment from the core or cores in the clear rinsing cycle, so that an at least partial escape of the core material into the clear rinsing cycle medium is possible.
Preferably the compound incorporates a polymer, preferably a pH-sensitive polymer, which comprises at least one repeat unit, which has at least one basic function, which is not part of the polymer backbone chain.
In a preferred embodiment the polymer comprises at least one repeat unit, which is based on a compound selected from the group comprising vinyl alcohol derivatives, acrylates or alkyl acrylates, which have said basic function.
According to the invention the polymer is a carbohydrate functionalized with said basic function.
The aforementioned basic function is preferably an amine and in particularly preferred form a secondary or tertiary amine.
In a preferred alternative the repeat unit is based on a compound with the following formula III: 
in which G is a linking group selected from xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94CONHxe2x80x94, NHCOxe2x80x94, xe2x80x94NHCONHxe2x80x94, xe2x80x94NHCOOxe2x80x94, xe2x80x94OCONHxe2x80x94or xe2x80x94OCOOxe2x80x94, R1, independently of one another, is hydrogen or an alkyl group with 1 to 3 carbon atoms, R2 independently of one another, hydrogen or an alkyl group with 1 to 5 carbon atoms and x is an integer from 1 to 6.
Preferably the repeat unit is based on a compound with the following formula IV: 
in which R1, independently of one another, is hydrogen or an alkyl group with 1 to 3 carbon atoms, R2, independently of one another, is hydrogen or an alkyl group with 1 to 5 carbon atoms and x is an integer from 1 to 6.
In a further embodiment the basic function is an imine or a basic, aromatic N-containing group, preferably a pyridine group or an imidazole group.
In a further embodiment the pH-sensitive polymer is derived from chitosan.
The invention finally proposes that the compound incorporates K-carrageenan.
In a special embodiment of the invention the core or cores comprise at least one material selected from the group constituted by surfactants, antibacterial compositions, silver protection agents, fragrances, bleaches, disinfectants, odour masking agents, anti-coating agents and enzymes.
The core or at least part of the cores can be in the form of an encapsulated liquid, preferably in the form of a liquid contained in a gelatin capsule.
According to a further embodiment the core or at least part of the cores is in solid form.
Preferably the core or at least part of the cores has a melting point of more than 35xc2x0 C., preferably between 55 and 70xc2x0 C.
The invention also relates to a process for performing a dishwashing cycle in a dishwashing machine, where the composition according to the invention is added at an appropriate time during the prerinsing cycle or main cleaning cycle to the medium in the dishwashing machine.
In a special embodiment of the invention for the case that the basic composition in the form of a tablet is not able, following its dissolving in the medium up to the end of the main cleaning cycle to make available a concentration of the specific compound in the medium which is sufficiently high in order to prevent a significant dissolving of the envelope and a significant detachment of the envelope from the core or cores, said adequate concentration of the specific compound is made available by adding a further composition such as e.g. a machine dishwashing agent composition, to the medium of the main cleaning cycle at an appropriate time.
The composition according to the invention is characterized in that it gives excellent results both in the main cleaning cycle and in the clear rinsing cycle of a dishwashing machine. The basic composition, e.g. in the form of a tablet, is dissolved during the main cleaning cycle and can evolve its corresponding action (cleaning, water softening, washing intensification, etc.). The particle according to the invention contains as the core material the substance or substances evolving their main function in the clear rinsing cycle of the dishwashing machine, e.g. clear rinsing agents.
Said substance or substances are protected by an envelope which, at the concentration of a specific compound, e.g. a specific ion such as OHxe2x80x94 ion (and therefore at a specific pH-value) and the temperature of the main cleaning cycle are stable and do not or only insignificantly dissolve or separate. Only when said concentration drops significantly by dilution, i.e. at the start of the clear rinsing cycle, is the solubility of the enveloping material reduced so significantly that it rapidly dissolves or separates and that the active core material is released in the surrounding medium. It is important that the protection of the core material acts from the addition of the inventive composition to the water up to the start of the clear rinsing cycle, i.e. before the cleaning liquor reaches a sufficiently high concentration of the specific compound, as will be explained hereinafter.
As an alternative to the tablet form of the basic composition used in preferred manner, other administration forms are possible and are covered by the protective scope of the invention. Thus, the particles with the envelope changing in the case of a modification of the concentration of the specific compound with respect to its solubility can be connected, e.g. enveloped with the basic composition by a granulation or similar process. In order to ensure for this embodiment an optionally desired, reduced contact between the envelope and the basic composition, the particles can be surrounded by a further protective jacket, which e.g. comprises a water-soluble compound independent of the concentration of the specific compound. With this embodiment during the main cleaning cycle initially the basic composition and protective jacket of the particles are dissolved and once again the particles protected by the inventive envelope are left behind.
Unless special charging or dosing aids are used for charging or dosing, which can retain the particles according to the invention, said particles must be chosen sufficiently large that they do not get discharged to a significant extent during the pumping out following the main cleaning cycle and intermediate rinsing cycle or cycles from the dishwashing machine.